A great many different interventional tools and techniques have been proposed over the years for treating narrowing, blockage, and other conditions of veins or arteries leading to insufficiency of blood flow. Endovascular techniques, as opposed to open surgery, are commonly used to minimize invasiveness of the procedure. A classic example is the percutaneous entry of a wire guide or the like into a vein or artery to be treated, followed by use of the wire guide to position a treatment device such as a stent, balloon, infusion catheter, or a variety of other mechanisms, at or near a location to be treated.
In navigating the circulatory system from a remote access site, wires, catheters and other interventional tools are commonly required to traverse a route having potentially numerous turns and junctions. Since an access site through a patient's skin can sometimes be as much as a meter or possibly even further from a target treatment location, a relatively high degree of skill and specialized tools are often required for successful access and treatment.
A given treatment location such as a narrowing or blockage as noted above, must often be crossed so that interventional tools can be successfully used at that location itself, or others further on. In some instances, wires can be used to push through a calcified lesion, fibrous thrombus cap or the like. In other instances, attempting to push a wire straight through may not be possible, or considered risky, due to the risk of puncturing the vascular wall. In such instances, clinicians may attempt to cross subintimally, via pushing a wire or the like through tissues forming the vascular wall, with the intention of reentering the true lumen of the vein or artery on the other side of the area bypassed.
A wide variety of different lumen reentry techniques have been proposed, some with a measure of success, such as a specialized deflectable hollow needle that punches its way from the subintimal layers back into the true lumen of the vein or artery, enabling a wire guide to navigate around a lesion with the eventual intention of forming a conduit for blood flow through the subintimal layers. U.S. Pat. No. 6,511,458 to Milo, et al, is directed to deflecting a wire advanced to a point distal to an occlusion back into a blood vessel lumen using a deflecting catheter advanced over the wire. After the wire is returned to the lumen, the catheter may be withdrawn and the wire is then available for introduction of other tools. Those skilled in the art will be familiar with the necessity of properly orienting a reentry tool such as that taught by Milo et al. For instance, if the catheter providing for delivery or placement of the reentry tool is not properly oriented, the tool might form a passage upon deployment out of the vein or artery, or through the subintimal tissues, rather than returning to the true lumen. Milo, et al appear to address this concern using a visualization subsystem of the catheter system, apparently some form of imaging or enhancement to imaging.